You're spotting something real when you notice those inconsistencies, but the gap between nailing a question and completely missing the point doesn't necessarily tell you which side of understanding/pattern matching the model fell on. Sometimes the model gets context wrong in ways that seem impossible if it "understood" anything - but then it'll handle a genuinely tricky multi-part question that requires reasoning across different domains, and you'd swear it comprehended what you meant.
The thing is, when you're on the outside looking in, you can't actually determine what's happening in the weights and activations. What you're experiencing - the hits and misses - would look identical whether the model had some genuine grasp of meaning or was just doing really, really sophisticated prediction based on statistical patterns. A human who misses the point of your question looks confused in a way a chatbot does too, but that's purely observable behavior. You're basically in the position of someone trying to figure out if another person understands you by only reading their responses, with no access to their brain.
If you want a practical approach instead of getting stuck on the philosophy: treat the inconsistency as a feature, not a bug. That randomness of quality is your cue to verify important stuff, ask follow-up questions to check whether it's tracking context, and not trust it for anything where being confidently wrong matters. Whether there's "understanding" happening underneath doesn't change how you should actually use these tools.